JP3164990B2 - Radioactive waste solidification equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for solidifying radioactive waste, and more particularly to an apparatus for solidifying radioactive waste with a solidifying material.

[0002]

2. Description of the Related Art Radioactive waste generated from nuclear power plants cannot be disposed of in drums. In order to dispose of radioactive waste, it is necessary to finally solidify the radioactive waste. The solidification of radioactive waste is generally performed as follows. First, a solidified material and water are mixed at a predetermined ratio to prepare a kneaded product of the solidified material and water, a so-called paste. For this preparation, a kneading tank equipped with a stirrer is used. The stirrer is provided at the center of the kneading tank in order to improve the mixing effect of the solidified material and water. Solidification material is usually
A hydraulic material such as cement and cement glass is used. Next, the paste is poured into a solidification container (drum) filled with radioactive waste. This paste gradually hardens in the drum and forms a solidified body.

[0003]

In the process of producing the paste in the kneading tank, it is inevitable that the paste adheres to the wall surface of the kneading tank and the stirrer to some extent. Once the paste adheres to those parts, it becomes easier to adhere one after another. Also, the attached paste hardens over time. There is a possibility that the mass of the attached paste may be peeled off due to mechanical vibration or the like. If the mass of the peeled paste is mixed in the paste, the paste may be blocked when the paste is discharged. Therefore, it is necessary to wash the inside of the kneading tank after discharging the paste. Wash water is injected into the kneading tank. Since the adhered paste is not easily dropped only by immersion in water, the washing water is stirred by turning a stirrer. By this washing, the paste adhered to the wall surface of the kneading tank and the stirring blade of the stirrer is removed. However, the paste adhering to the rotating shaft of the stirrer at the center of the kneading tank is difficult to drop.

[0004] It is an object of the present invention to provide a radioactive waste solidification treatment apparatus capable of improving the cleaning property of the rotating shaft of a stirrer.

Another object of the present invention is to provide an apparatus for solidifying radioactive waste capable of increasing the effect of cleaning the rotating shaft of a stirrer.

[0006]

SUMMARY OF THE INVENTION To achieve the above object, a feature of the present invention is that a kneading tank to which a solidifying material and water are supplied, and a rotary shaft is provided vertically in the kneading tank, and A stirrer that stirs the solidified material and water to form a paste; a unit that supplies the paste generated in the kneading tank to a solidification container filled with radioactive waste; and a washing water in the kneading tank. Means for supplying, and means arranged in the kneading tank and attached to the kneading tank, for changing the circumferential flow of the liquid generated by the rotation of the stirrer toward the center of the kneading tank. That is.

[0007] A feature of the present invention that achieves the above-mentioned other object is that, in addition to the above-mentioned features, means for changing the flow of the liquid is arranged near a wall surface in the kneading tank.

[0008]

The means for changing the circumferential flow of the liquid generated by the rotation of the stirrer to the flow toward the center of the kneading tank is disposed in the kneading tank and attached to the kneading tank, so that the stirring is performed with a simple structure. The cleaning performance of the rotating shaft of the machine can be improved.

Since the means for changing the flow of the liquid is arranged near the wall surface in the kneading tank, the cleaning action of the rotating shaft is increased by applying the washing water having a high flow velocity near the wall surface of the kneading tank to the rotating shaft.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has been made by investigating the cause of the inability to wash the paste adhered to the rotating shaft of the stirrer in the prior art. The details of the experiment will be described.

The experiment was carried out using a kneading tank 2 with a standard paddle-type stirrer having a volume of 200 liters used in the conventional example. A stirrer 24 having a rotating shaft 4 and a stirring blade 3 attached to the rotating shaft 4 is provided in the kneading tank 2. The rotating shaft 4 is attached to the motor 20. First,
40 kg of water was injected into the kneading tank 2. At this time, the state in the kneading tank 2 is as shown in FIG. Since the stirrer 24 is not rotating, a part of the rotating shaft 4 of the stirrer 24 is
Immersed in. Thereafter, the stirrer 24 was rotated at 90 rpm. The water 23 in the kneading tank 2 is swirled by the stirring blade 3 and moves toward the wall surface of the kneading tank 2 by centrifugal force. This phenomenon occurs because the water 23 in the center of the kneading tank 2 where the rotating shaft 4 is located.
Is lowered, and the liquid level on the wall surface side is increased from the state shown in FIG. 4 (see FIG. 5). In this state, 120 kg of cement glass as a solidifying material is supplied into the kneading tank 2. It was observed that a part of the cement glass adhered to the lower portion of the rotating shaft 4 wet in the state of FIG. 4 to form a paste. A portion 25 in FIG. 5 is a portion where the cement glass adheres and becomes a paste. The cement glass and the water 23 are kneaded by the stirring of the stirrer 24, and a paste is generated in the kneading tank 2. Even during the kneading of the paste by the stirrer 24, the paste moves to the wall surface side of the kneading tank 2 as shown in FIG.

After the paste was discharged from the kneading tank 2, 90 liters of washing water was supplied into the kneading tank 2. In a state where the agitator 24 is not rotated and the washing water in the kneading tank 2 is stationary, a paste-like cement glass adhered to a lower portion of the rotating shaft 4,
Also, it was found that the paste adhered to the wall surfaces of the stirring blade 3 and the kneading tank 2 was hard to drop. When the stirrer 24 is rotated, the washing water is biased toward the wall surface of the kneading tank 2 as shown in FIG. Further, the flow rate of the washing water in the kneading tank 2 during the stirring increases near the wall surface but decreases near the rotating shaft 4. For these reasons, it was found that the paste attached to the lower portion (25) of the rotating shaft 4 could not be washed. However, by rotating the stirrer 24 in the kneading tank 2 filled with the washing water, the paste adhering to the inner surface of the kneading tank 2 and the stirring blade 3 can be sufficiently removed.

Therefore, washing water was supplied into the kneading tank 2, and the driving and stopping of the stirrer 24 were repeated. When the stirrer 24 stops, the liquid level near the rotation axis rises and the rotation axis 4 comes into contact with the washing water. However, since the swirling flow rate of the washing water at the center of the kneading tank 2 was small, the paste attached to the rotating shaft 4 did not drop much.

Further, cleaning of the lower portion of the rotary shaft 4 was attempted by using cleaning water sprayed from a spray nozzle 26 attached to the tip of a cleaning water supply pipe 27. However, unless the spray nozzle 26 is brought close to the rotating shaft 4, the paste adhering to the rotating shaft 4 cannot be sufficiently removed. When the spray nozzle 26 is installed close to the rotating shaft 4, the paste adheres to the spray nozzle 26 during kneading, and the spray nozzle 26 is closed.

Next, washing water (see FIG. 5) which is generated while the agitator 24 is rotating and is deflected toward the wall surface of the kneading tank 2 is supplied to the kneading tank 2.
Thought about returning to the center. For this reason, a plate (a baffle plate) was arranged near the wall surface of the kneading tank 2 so as to block the flow of the washing water at the deflected portion. This baffle is located above the rotor 4. The rotating machine 24 is driven while the washing water is supplied into the kneading tank 2. Part of the washing water that has drifted to the wall surface of the kneading tank 2 hits the baffle plate and flows in the flow direction toward the center of the kneading tank 2. The flow toward the center is the rotation axis 4
It was confirmed that the cleaning effect at the lower part of the rotating shaft 4 was improved.

An embodiment of the present invention based on the above experimental results will be described below.

An apparatus for solidifying radioactive waste according to a preferred embodiment of the present invention will be described below with reference to FIG. This embodiment can be applied to a case where radioactive waste generated from a nuclear power plant is solidified with a solidifying material.

The solidified material hopper 5 filled with cement glass as the solidified material is connected to the V-shaped kneading tank 2 via the rotary feeder 7, the solidified material measuring container 6, and the rotary feeder 17. The kneading tank 2 has an inner diameter of 90 cm,
The height is 60 cm and the volume is 200 liters. The added water measuring container 8 to which the added water is supplied is connected to the kneading tank 2 via a valve 9. A discharge pipe 13 is connected to the bottom of the kneading tank 2. A valve 18 and a three-way valve 12 are provided in the discharge pipe 13. A pipe 14 connected to the three-way valve 12 is connected to a washing water tank 15. A washing water supply pipe 21 having a pump 16 and a valve 19 connects the washing water tank 15 and the kneading tank 2. A stirrer 24 having a rotating shaft 4 and a stirring blade 3 attached thereto is provided in the kneading tank 2. Rotary axis 4
Is connected to the motor 20. The side wall of the kneading tank 2 is cylindrical, and the bottom connected to the side wall has an inverted conical shape. The stirring blade 3 is also V-shaped. As shown in FIG. 2, the baffle plate 1 is located perpendicular to the side wall in the kneading tank 2 and is provided at one position in the circumferential direction of the kneading tank 2. Baffle board 1
Has a width of 70 mm and a thickness of 5 mm, and is located above the stirring blade 4 so as not to hit the rotating stirring blade 4. The upper plate 22 located at the upper end of the kneading tank 2 has an inspection port 23 right above the baffle plate 1. The baffle plate 1 covers the inspection opening 23 and the upper plate 2
2 attached to the cover.

Radioactive waste 11 generated at a nuclear power plant
Will be described. A paste is created in the kneading tank 2. Preparation of this paste is performed as follows. First, a predetermined weight (for example, 40 wt.
kg) of water is supplied into the kneading tank 2 by opening the valve 9. The agitator 24 is rotated at 90 rpm. In this state, the rotary feeder 7 is opened, and the cement glass in the solidified material hopper 5 is supplied into the solidified material measuring container 6.
When a predetermined weight (for example, 120 kg) of cement glass is supplied into the solidified material measuring container 6, the rotary feeder 7
Is closed, and the rotary feeder 17 in the closed state is opened. A predetermined weight of cement glass is supplied into the kneading tank 2 via the rotary feeder 17. The cement glass and water in the kneading tank 2 are mixed by the stirring blade 3 to generate a paste. After supplying the cement glass, the mixture is stirred for 10 minutes. The prepared paste is injected into the drum 10, which is a solidified container filled with radioactive waste (eg, pellets) 11 through the discharge pipe 13 by opening the valve 18. At this time, the three-way valve 12 does not connect the discharge pipe 13 and the pipe 14. When continuously injecting the paste into the plurality of drums 10, the above operation is repeated.

After the paste in the kneading tank 2 is completely discharged into the drum 10 through the discharge pipe 13, the inside of the kneading tank 2 is washed. First, the valve 19 is opened and the pump 16 is driven to supply 90 liters of washing water in the washing water tank 15 from the washing water supply pipe 21 into the kneading tank 2. In this case, the lower part of the rotating shaft 4 of the stirrer 3 to which the paste is adhered, the stirring blade 3 and the wall surface of the kneading tank 2 are immersed in the washing water.
When the stirrer 3 is stopped and the washing water is stopped, the attached paste does not fall. Therefore, the stirrer 3 is rotated at 90 rpm. The washing water in the kneading tank 2 moves to the vicinity of the wall surface of the kneading tank 2 by centrifugal force. A part of the washing water that has drifted to the vicinity of the wall surface hits the baffle plate 1 as shown in FIG. This flow also hits the lower part of the rotating shaft 4, so that the lower part of the rotating shaft 4 can be sufficiently cleaned.
After the washing, the washing water in the kneading tank 2 is discharged to the discharge pipe 13 and the pipe 1
4 and is discharged to the washing water tank 15. At this time,
The three-way valve 12 connects the discharge pipe 13 and the pipe 14.

As described above, according to the present embodiment, by providing the baffle plate 1 having a simple structure, the lower portion of the rotary shaft 4 which has conventionally been difficult to clean can be sufficiently cleaned. The paste adhering to the rotating blades 3 and the inner wall of the kneading tank 2 can be removed by rotating the stirrer 24. Since the baffle plate 1 is attached to the cover that covers the inspection port 23, the baffle plate 1 can be easily attached and detached. Therefore,
Maintenance of the baffle plate 1 is easy. Also, baffle plate 1
Is located near the wall surface of the kneading tank 2 where the flow rate of the washing water generated when the stirrer 24 rotates is large, so that the flow rate of the cleaning liquid toward the rotating shaft 4 is also large, so that the cleaning effect of the rotating shaft 3 is enhanced.

By providing the baffle plate 1, the flow of the paste at the time of kneading the paste also collides with the baffle plate 1 and flows inward, so that kneading is sufficiently performed. For this reason, the kneading time can be shortened. When the paste flow collides with the baffle plate 1, the paste easily adheres to the rotating shaft 4.
, The paste attached to the rotating shaft 4 can be removed.

As described above, the attachment of the baffle plate to the kneading tank makes it possible to wash the paste adhered to the rotating shaft 4 of the stirrer 24, which was conventionally difficult to wash.

FIG. 7 shows the cleaning effect of the rotating shaft of the agitator 24 when the insertion depth of the baffle plate 1 into the cleaning water is changed during cleaning. The results are as follows. A cement glass paste was prepared in the kneading tank 2 under the conditions shown in the embodiment of FIG. 1, and after discharging this, 90 liters of washing water was supplied to the kneading tank 2 and the stirrer 24 was rotated at 90 rpm. It is when it is rotated. The insertion depth of the baffle plate 1 into the washing water is the depth from the liquid level to the lower end of the baffle plate 1 in a state where the washing water is stationary in the kneading tank 2 (FIG. 4). The effect of cleaning the rotating shaft is a relative value of a measured value of the amount of paste remaining on the rotating shaft 4 of the stirrer 24 after the stirrer 24 is rotated for 5 minutes. As the insertion depth of the baffle plate 1 increases, the flow of the washing water that hits the rotating shaft 4 gradually increases, and the range in which the washing water hits the rotating shaft 4 also widens. When the insertion depth of the baffle plate 1 is 50 mm, these effects are maximized, and the cleaning effect at this time is maximized. On the other hand, when the insertion depth exceeds 50 mm, the cleaning effect gradually decreases.

FIG. 8 shows the result of examining the effect of cleaning the rotating shaft 4 of the stirrer 24 by changing the insertion angle of the baffle plate 1 during cleaning. This shows a relative measurement value of the amount of the paste remaining on the rotating shaft 4 of the stirrer 24 while changing the insertion angle of the baffle plate 1 under the same conditions as in FIG. The insertion angle of the baffle plate 1 is 0 degree in the vertical direction with respect to the flow of the wash water, and the flow direction side of the wash water is a minus angle on the basis of this 0 degree and the side opposite to the flow of the wash water is plus. Expressed as an angle.
When the insertion angle of the baffle plate 1 is changed from a positive angle toward 0 degree (to be perpendicular to the side wall of the kneading tank 2), the ratio of the washing water corresponding to the rotating shaft 4 of the stirrer 24 gradually increases. , +10 degrees, the cleaning effect is maximized. This is because, since the washing water has a flow velocity due to rotation, by tilting the insertion angle of the baffle plate 1 in a direction against the flow, the ratio of the washing water that hits the rotating shaft 4 of the stirrer 1 increases. On the other hand, when the insertion angle of the baffle plate 1 becomes smaller than +10 degrees, the ratio of the washing water that hits the rotating shaft 4 of the stirrer 24 gradually decreases, and the washing effect decreases.

[0026]

According to the present invention, the means for changing the circumferential flow of the liquid generated by the rotation of the stirrer to the flow toward the center of the kneading tank is provided in the kneading tank and attached to the kneading tank. Therefore, the cleanability of the rotating shaft of the stirrer can be improved with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an apparatus for solidifying radioactive waste according to a preferred embodiment of the present invention.

FIG. 2 is a plan view of the kneading tank of FIG.

FIG. 3 is an explanatory diagram showing a flow state of washing water in a kneading tank of FIG. 1;

FIG. 4 is an explanatory diagram showing a state in which cleaning water is supplied into a kneading tank.

FIG. 5 is an explanatory diagram showing a flow state of the washing water when the washing water is supplied into the kneading tank and the stirrer is rotated.

FIG. 6 is an explanatory diagram showing a state in which cleaning water is injected from a spray nozzle provided in a kneading tank.

FIG. 7 is a characteristic diagram showing the effect of cleaning the rotating shaft of the stirrer when the insertion depth of the baffle plate into the cleaning water is changed during cleaning.

FIG. 8 is a characteristic diagram showing the effect of cleaning the rotating shaft of the stirrer by changing the insertion angle of the baffle plate during cleaning.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Baffle plate, 2 ... Kneading tank, 3 ... Stirring blade, 4 ... Rotary axis, 5
... solidified material hopper, 6 ... solidified material measuring container, 7, 17 ... rotary feeder, 8 ... additive water measuring container, 10 ... solidified container, 11 ... radioactive waste, 13 ... discharge pipe, 15 ... washing water tank, 16 ... Pump, 21: washing water supply pipe.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shin Tamada 3-1-1, Sachimachi, Hitachi-shi, Ibaraki Pref. Hitachi, Ltd. Hitachi Plant (72) Yoshimasa Kiuchi Inventor 3--2, Sachimachi, Hitachi-shi, Ibaraki No. 2 Inside Hitachi Engineering Services Co., Ltd. (72) Inventor Takao Kobayashi 3-2-1, Kochi-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Engineering Co., Ltd. (72) Hiroyuki Tsuchiya 3-2-2, Kochi Town, Hitachi City, Ibaraki Prefecture 2 Hitachi Nuclear Engineering Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) G21F 9/30 G21F 9/16

Claims (3)

(57) [Claims] 1. A kneading tank to which a solidifying material and water are supplied, and a stirrer which has a rotating shaft provided vertically in the kneading tank and stirs the solidifying material and water in the kneading tank to form a paste. When,
A means for supplying a paste generated in the kneading tank to a solidification container filled with radioactive waste, a means for supplying washing water to the kneading tank, and a means for disposing in the kneading tank and attached to the kneading tank Means for changing a circumferential flow of the liquid generated by rotation of the stirrer to a flow toward the center of the kneading tank. 2. The apparatus for solidifying radioactive waste according to claim 1, wherein the means for changing the flow of the liquid is configured to be detachably attached to the kneading tank. 3. The apparatus for solidifying radioactive waste according to claim 1, wherein the means for changing the flow of the liquid is disposed near a wall in the kneading tank.